An apparatus of this kind is known from U.S. Pat. No. 5,505,567, in which a closed pneumatic conveyor circuit is provided, which extends between the conveyor housing, a centrifugal cyclone separator and a blower. Beneath the extruder, there is a flap in the conveyor housing, which can be opened if the extruder produces unwanted products, such as when starting up the extrusion process. A disadvantage here is that the flap opens up the entire system to the surroundings, as a result of which the gas used for the pneumatic transport within the system can escape, and ambient air can enter the system. A further disadvantage is that it is difficult to recover the heat released from the extruded material, since the system contains air and the moisture contained therein cannot readily be condensed.
The object of the invention consists in improving an extrusion and conditioning apparatus of this kind such that, when starting up the system, if the extruder produces unwanted product, it is ensured that the pneumatic conveyor system per se remains closed and without contact with the surroundings.
A further object consists in creating a possibility of unproblematically recovering the heat introduced into the system by the extruder.